Barrett's esophagus is a condition in which the normal stratified squamous epithelium of the esophagus is replaced by a metaplastic columnar epithelium. It develops as a complication of chronic gastroesophageal reflux disease and predisposes to the development of adenocarcinomas of the esophagus and gastric cardia. Barrett's associated adenocarcinomas are the most rapidly increasing cancers in the United States, but they are rarely discovered in time for Cure. Intensive endoscopic biopsy surveillance of patients with Barrett's esophagus can detect early, potentially curable Barrett's adenocarcinomas, but such surveillance is costly and time consuming. Dietary recommendations including a low-fat diet and weight reduction are an accepted part of standard medical therapy for patients with gastroesophageal reflux and Barrett's esophagus, but the efficacy of this diet in reversing intermediate endpoints of neoplastic progression in Barrett's esophagus and decreasing symptoms and mucosal damage associated with reflux has never been established in a randomized, clinical trial. The specific aims of this application for a cooperative agreement are to determine whether a dietary intervention to reduce the intake of dietary fat, increase the intake of fruits and vegetables, and reduce weight can l) reverse intermediate endpoints of neoplastic progression (increased G1 and S phase fractions) in Barrett's esophagus, and 2) lead to partial regression of premalignant metaplasia (as evidenced by the development of islands of normal squamous epithelium in the metaplastic columnar epithelium).